The present invention concerns light grids for measuring objects and securing dangerous zones around machines.
German patent document DE 694 07 784 T2 discloses a system for determining and judging the type and position of an object which passes one or more rays and interrupts them. The system includes means for generating a matrix of rays. The rays cross each other to form a network-like array of rays. In addition, this system generates information concerning one or more rays that were interrupted by an object and an analyzer which receives this information and from it determines the general type and position of the object that interrupted the rays. The analyzer constructs a space from the information which is bordered by uninterrupted rays inside of which the intruding object lies so that its shape and size can be determined with an acceptable approximation.
This system for detecting and judging the type and position of an object has significant drawbacks. The system uses narrow, focused rays for sensing. Such narrow, focused rays are disadvantageous because they require precise alignments. For the rays to reach the receiver, a precise alignment is a necessity. If the receiver or the light emitter of the system becomes misaligned, the system becomes unusable until it has been realigned.
Further, the light emitter and receiver are alternatingly arranged next to each other. This requires costly controls for operating the emitters and receivers. For example, the results from the individual receivers must be transmitted to an analyzer for further use. Addressing the individual emitters is also costly, because they are arranged on different support bars.